Relationship between the cause of obstruction in congenital hydronephrosis and changes in dilation of the fetal renal pelvis over time

BACKGROUND: Despite the implementation of intrauterine and postnatal ultrasound screenings, a significant number of cases of congenital hydronephrosis are detected in children of preschool age and older. It means that the period of development of hydronephrotic transformation varies in patients. This makes relevant the study of the relationship between the cause of obstruction and the rate of the renal pelvis dilation.
AIM: To determine the dynamics of the increase in the size of the renal pelvis in fetuses and infants with different causes of congenital hydronephrosis.
MATERIALS AND METHODS: A retrospective analysis covered 134 protocols of intrauterine ultrasound examinations and 74 postnatal preoperative ultrasound examinations of the kidneys of children who underwent surgery for various causes of congenital hydronephrosis. The Wilcoxon signed-rank test was used to assess the statistical significance of the studied variables. A correlation and regression analysis of the relationship between the cause of obstruction and the rate of dilation of the fetal renal pelvis was performed using the Pearson correlation coefficient. The strength of the relationship between the studied features was assessed using the Chaddock scale.
RESULTS: A correlation and regression analysis of the dependence between the fetal renal pelvis size and an increase in the gestational age by a week (within the range of 20.5–32.5 weeks) revealed the following patterns: in fetuses with stricture of the ureteropelvic junction, the pelvis of the affected kidney increased by 0.6 mm per week; in fetuses with obstruction by an aberrant blood vessel, by 0.35 mm per week; in fetuses with embryonic adhesions, by 0.2 mm per week; in fetuses with a high 
ureteral origin, by 0.23 mm per week.
CONCLUSIONS: During the 2nd and 3rd intrauterine screening, the probability of prenatal diagnosis of fetal pyelectasis due to adhesions in the ureteropelvic junction and high ureteral origin is significantly lower than in case of stricture and obstruction by an aberrant blood vessel. Changes over time in dilation of the fetal renal cavity system and its size help suggest the cause of obstruction of the ureteropelvic junction and pre-estimate the fetal renal pelvis size at the time of delivery; if advanced stage hydronephrosis is expected, this allows choosing an institution for delivery to provide percutaneous nephrostomy for the newborn.